1. Field of the Invention
The present invention relates to a device for the manipulation of workpieces for a bending press which includes a cooperating die and punch.
2. Description of Prior Art
Bending presses which include horizontally elongate dies and punches, one of which is movable vertically relative to the other, are widespread.
A very simple bending press includes a lower movable die and an upper fixed punch against which the die is thrust in order to bend pieces of sheet metal through a particular angle. The bend may have a sharp edge or a curved-line, undulating-line, broken-line or mixed-line profile. Most commonly, however, the die and the punch form a dihedral normally for forming right-angled bonds. They are used to make a succession of parallel bends in a workpiece of sheet metal which is usually rectangular, so as to finish up with a workpiece having a square C-section, a square omega-section or a Greek-key section.
The manipulation of the workpieces in order to make the successive bends is effected manually by two or more operators, with considerable labour costs.
Certain profiles which have bends all in the same sense, such as a square C-section, may in some cases be formed with the same side of the workpiece always being presented to the press. However, after the first bend of the C has been made, the operators sometimes have difficulty in introducing the same side of the workpiece between the die and the punch and are forced to turn the workpiece around horizontally to its other side before making the second bend. This operation requires considerable space in front of the press.
If the profile of the workpiece has bends in opposite senses, there are two solutions which may be adopted in the event that it is not possible to change the die and the punch of a press: the first solution is to use two presses beside each other, one for bending in one sense and the other for bending in the other sense; the second solution consists of using a single press and rotating the workpiece through 180.degree. each time the sense of bending is changed. In this case, the workpiece is sometimes rotated about a longitudinal axis parallel to the bends; sometimes, however, the workpiece is turned "end over end" or rotated about an axis perpendicular to the bends.
The first solution is expensive in that it requires two presses instead of only one. The second solution has rather long manipulation times with the consequent costs, and requires a lot of space, in addition to the fact that the turning over of a large and heavy sheet of metal is a dangerous operation.